I would wait for a warmer day. At least sunny with very little wind, and work quickly. If the bees are actively flying, that is a good sign for a potentially suitable day too.
Here in NJ it is time to pull all harvestable honey and deal with mites. Once your mites are dealt with, and based on method used, you can hope for a fall flow of goldenrod and asters. Try and leave at least 60-80 lbs of honey for the bees.
I will use Oxalic Acid and the “dribble” method on the frames. Just watched a You Tube video on it. You have to get the mixture right with the sugar water. I was also considering the vapor method with the OA. This is our first year with the bees and am learning a lot.
Just looked it up. Nice. I will try that this year too!
Prepare solution
Measure 600 ml of hot water into a non-reactive container.
Add 35 grams of oxalic dihydrate crystals (wood bleach) into the hot water. Stir but do not shake.
When the crystals are dissolved, add the 600 grams of sugar. Stir until dissolved.
Apply the solution
Smoke your bees down between the frames.
Dip the end of your syringe into the medicated syrup and pull back the plunger, filling the syringe to the 50 ml mark.
Starting at one end of the frames, dribble 5 ml of the solution along a seam that contains bees. (I like to start at the far end and dribble toward me.)
Once you have dribbled 5 ml, you must go on to a new seam. (A seam is the space between two frames or the space between a frame and a sidewall.)
After each seam of bees gets 5 ml of solution, you are done.
In any case, you cannot go over 50 ml per colony. If the hive has more than 10 seams, dribble where the most bees are. Alternately, you can give less than 5 ml per seam and do more than 10 seams, but you cannot go over 5 ml in any one seam or 50 ml total per colony.
Remember to apply the mixture directly onto the bees. Mixture that lands on the woodenware will be ignored by the bees and not moved throughout the colony.
I would far prefer vapor (OAV) at this time of year. The dribble works best on broodless hives when it is cold enough for the bees to cluster. You will only get the phoretic mites (those on the surface of bees) with a dribble - it can’t get into the capped brood where the majority of the mites are located. OAV can’t get into the brood either, but it is very quick to do and can be repeated at 5 day intervals to really disrupt the mite life cycle and knock the numbers down.
If you don’t want to invest in a vape setup, Apivar or Apiguard would be my other choices, assuming the super is off. But you will need to rotate treatments to avoid resistance, so I would just get the stuff to vape. It works out cheaper in the end, anyway.
I am a bit naughty, and use OAV even when there is a nectar flow on. Be aware that my method is not EPA-approved!
Take the super off the hive and put it on one side. Replace the inner cover and roof.
Block the entrance with a tea towel and vape (mine takes about 6 minutes for a double deep dose of OAV).
Remove the vaping iron and dunk in a pot of cold water, leaving the tea towel in place.
Wait 10 to 15 mins for the vapor to precipate.
Remove the tea towel.
Take the inner cover off and put the super back on. Close up the hive.
Repeat again 5 days later, and again 5 days after that.
The reason I think this is safe to do is that OAV condenses/precipitates very quickly. By the time the super goes back on, there isn’t any floating around in the hive which could get into the super. There may be a bit on the bees, but not enough to contaminate the honey, and some oxalic acid is naturally present in honey anyway. I know of plenty of people in Europe who use this method too, and have never had a problem. Your risk if you choose to do it.